This invention relates generally to a process for making prescription eyeglass lenses, and particularly to an axis block assembly applicable for use in one or more lens processing stations.
In general terms, prescription eyeglass lenses are made from a toric or cylindrical ophthalmic, lens blank having an essentially concave lens surface and an opposing convex surface. The convex surface of the lens blank is mounted on a lens block using a heated bonding medium, such as liquid wax, which hardens when cooled to join the lens blank and lens block together. The concave lens surface is exposed for processing. The joined lens block and lens blank are then moved to a lens cutting machine which cuts the lens surface to a Shape corresponding to a given prescription. After cutting, the lens block and lens blank are moved to a surface finishing or "lapping" machine where the cut lens surface is smoothed and polished. The lapping machine includes a lap tool which moves over the lens surface in a high-speed, generally elliptical orbit.
The axis block assembly of the present invention facilitates loading of the lens block and lens blank in the lapping machine, and provides for forward and rearward pivoting movement and side-to-side movement of the lens block and lens blank during actuation of the lap tool. According to one prior art assembly, the block holder allows slight movement of the lens block and lens blank in a side-to-side direction, but restricts pivoting movement in a forward and rearward direction. Because of the generally elliptical orbit of the lap tool and the restricted movement of the lens block and lens blank, the block holder experiences a substantial amount of wear over a relatively short period of use. Frequent replacement of the block holder is time consuming and expensive. Furthermore, the prior art block holder requires the operator to manually hold the lens block as the block holder moves from the raised loading position to an operative position adjacent the lap tool. This process can result in misalignment of the lens blank over the surface of the lap tool, and can cause injury to the fingers of an inattentive operator.